1. Field of the Invention
The present general inventive concept relates to an image reading device and an image forming apparatus having the same, and more particularly, to an image reading device, an image forming apparatus having the same, and methods thereof that are capable of achieving duplex scanning of a document.
2. Description of the Related Art
An image forming apparatus is an apparatus that prints an image on a printing medium, e.g., paper, according to an inputted image signal. An image forming apparatus is classified as a printer, a copying machine, a multi-function printer that has multiple functions of printing, copying and scanning, and the like. For example, a multi-function printer can perform a printing function of printing an image in response to image information from an external apparatus such as a computer, etc., a reading function of reading image information recorded on a document, a copying function of printing an image in response to scanned image information, and a fax function of transmitting scanned image information to a remote place through communication links.
In order to achieve the above functions, a multi-function image forming apparatus is equipped with an image reading device. An example of a prior art image reading device is disclosed in U.S. Pat. No. 5,430,536.
The disclosed prior art image reading device includes an input tray on which a document to be scanned is loaded, an output tray on which the scanned document is loaded, and a U-shaped document path that is formed between the input tray and the output tray. Image information recorded on one surface of the document passing through the document path is scanned by a raster input scanner (RIS). The disclosed prior art image reading device further includes a duplex document path that connects a downstream side of the RIS and an upstream side of the RIS to achieve the duplex scanning. In the duplex scanning operation, the document fed toward the output tray after one surface (e.g., a first surface) is scanned is reversely fed at a specific point of time to pass through the duplex document path. The document having passed through the duplex document path passes again through the document path so that the other surface (e.g., a second surface) is scanned.
In such a duplex scanning operation, if the document is discharged immediately after the first and second surfaces are scanned, the documents are piled unevenly on the output tray such that a user has difficulty in arranging the documents. To solve this problem, the prior art image reading device is configured not to discharge the document immediately after scanning the first and second surfaces of the document in the duplex scanning operation but to reversely circulate the document one more time to sort the duplex scanned documents in page order.
However, it is practically inefficient to circulate the duplex scanned document one more time just for the page sorting. Further, the additional reversal and circulation of the document cause a considerable decrease in the duplex scanning speed.
Also, in the disclosed prior art image reading device, the document that is reversely fed after the first surface is scanned or the document that is reversely fed for the page sorting may interfere with the document loaded on the output tray. Such interference between the document fed reversely and the document loaded on the output tray may cause problems in that the scanning operation is not achieved smoothly and the document loaded on the output tray may be drawn back into the image reading device together with the document that is reversely fed.